R Notes for Topic 8: Measures of Center
R notes for Activity 8-2: Game Show Prizes
You can use the following command to make the vector of deal amounts.
DealAmounts = c(0.01, 1, 5, 10, 25, 50, 75, 100, 200, 300, 400, 500, 750,
1000, 5000, 10000, 25000, 50000, 75000, 100000, 200000, 300000,
400000, 500000, 750000, 1000000)
You can use mean to compute the
mean of a vector and median to compute
the median of a vector.
R notes for Activity 8-3: Matching Game
Although the book says that the data are stored in the file
Matching, we've separated the data into
three separate files:
MonopoloyPrices.csv,
SnowfallAmounts.csv,
and
QuizPercentages.csv.
All are stored in the standard data directory for this course.
Recall that you can read a file into a frame with a command like
MonopolyPrices = read.csv("/home/rebelsky/Stats115/Data/MonopolyPrices.csv")
You should be able to figure out the commands to read the other two
data sets.
We need to load an appropriate library to do dotplots, but otherwise
it remains straightforward. Particularly since we do not plan to use
these graphs for anything but a quick observation, we don't even need
to fool with axis labels.
library(BHH2, lib="/home/rebelsky/Stats115/Packages")
dotPlot(MonopolyPrices, main="Prices of Monopoly Properties")
You might note something a bit strange about this command.
Traditionally, we use dotPlot with vectors.
And, if you think about it carefully, MonopolyPrices is
a data frame, rather than a vector. So, why does the command work?
Apparantly, R is smart enough to treat a data frame with one column
as a vector, at least for this plot.
If, however, you want to create a histogram, you'll need to
extract the column (which is also called
MonopolyPrices).
hist(MonopolyPrices$MonopolyPrices)
Here's a fine-enough grained histogram that it replicates the dotplot.
hist(MonopolyPrices$MonopolyPrices, breaks=seq(from=0,to=500,step=25))
As you already know, you can get the mean and median separately
with mean and median.
You can also get them together with a host of other information
by using summary.
summary(MonopolyPrices)
R notes for Activity 8-4: Rowers' Weights
The data are now stored in Rowers04.csv. You can read
them in as follows:
Rowers = read.csv("/home/rebelsky/Stats115/Data/Rowers04.csv")
Refer to the instructions from a previous activity to see how to make
dotplots and how to have R compute a mean and median. In each case,
you want to use the vector Rowers$Weight.
This activity asks you to remove one row (corresponding to
Cipollone, the coxswain) and, later, to change the
weight of Schroeder. It turns out that you need different tools
for the two activities. To delete rows, you use the row selection
commands. For example,
Rowers = Rowers[Rowers$Name != "Cipollone",]
To change weight use the fix command.
fix(Rowers)
Remember that R pauses while you're editing the
data set, so you must close the editing window before doing
anything else.
R notes for Activity 8-5: Buckle Up!
This activity requires a bit more work with R than we've done in
previous exercises. We start by reading in values.
SeatBeltUsage = read.csv("/home/rebelsky/Stats115/Data/SeatBeltUsage05.csv")
The first step is to separate the table into two parts.
Primary = SeatBeltUsage[SeatBeltUsage$LawType == "Primary", ]
Secondary = SeatBeltUsage[SeatBeltUsage$LawType == "Secondary", ]
You will need to extract the CompliancePercentage
column from each in order to compute dot plots, means, and medians.
dotPlot(Primary$CompliancePercentage)
summary(Primary$CompliancePercentage)
It may be helpful to draw each dot plot in a separate window.
In R, the way we create a new output window depends on the
computer system we're using. On Linux (which we use in class),
the command is X11(). On a Mac, the command is
quartz(). On Microsoft windows, the command is
windows(). Hence, on our Linux boxes, you might
create new windows for the two new plots with.
X11()
dotPlot(Primary$CompliancePercentage)
X11()
dotPlot(Secondary$CompliancePercentage)
R notes for Activity 8-17: Marriage Ages
You can load the data for this activity with
MarriageAges = read.csv("/home/rebelsky/Stats115/Data/MarriageAges.csv")
Since this is a homework activity, the remaining instructions are left
for you to determine.
R notes for Activity 8-18: Quiz Percentages
As you may recall from Activity 8-3, you can load the data for this
activity with
QuizPercentages = read.csv("/home/rebelsky/Stats115/Data/QuizPercentages.csv")
Since this is a homework activity, the remaining instructions are left
for you to determine. (Recall that you can use
fix to change the data.
